Falling film-evaporators and rotor structure therefor



Aug. 10, 1965 E. KELLER 3,199,574

FALLING FILM-EVAPORATORS AND ROTOR STRUCTURE THEREFOR Filed Nov. 13, 1961 INVENTOR.

United States Patent 3,19%,574 FALLING FHM-EVAiURATGRS AND RGTGR STRUCTURE THEREFGP.

Emil Keller, Zurich, wimerland, asaignor to Lewis A.G., Zurich, Switzerland Filed Nov. 13, 1961, Ser. No. 151,671 Claims priority, application Switzerland, Nov. 14, race, 12,729/653; Germany, Nov. 2, 1961, L 4tl,37l 5 Claims. (fll. 159-6) This present invention relates generally to an apparatus for the processing of fluid or fluent materials, such as an evaporating and concentrating apparatus for fluids or liquids which is a falling film type of evaporator. The processing apparatus ofthe present invention is particularly noteworthy in its new and improved rotor construction which comprises both relatively fixed and relatively which there is provided an apparatus for directly or indirectly influencing the temperature of the wall of the hou ing and the material to be processed which is lying thereagainst, as by heating or cooling, Whereas, on the inner wall side of the housing flowable or fluent material to be processed, as for example, fluids, liquids, pastes, granular, pulverant or like substances are applied in a relatively thin layer to the inner housing wall to form a free-falling film which is directed in the axial direction.

'Such is carried out in order to expose the material to a heat exchange eiiect, for example, to achieve an evaporation of solvents or the'lilre contained in the fluent material to be processed, or for the purpose of cooling during the performance of an exothermic reaction. The fluent or fluid material is applied to the inner wall of the tubular housing in the form of a thin layer by means of a coaxially arranged and rotatable rotor member.

For convenience in description the term fluid medium or material as employed hereinafter should be understood to embrace any and all such materials which can be treated with the apparatus of the present invention, as for example, of the type previously enumerated. Free falling evaporators or evaporators as employed in the narrower sense, that is to say, such constructions in which the solvents or otherwise contained in the fluid material are to be evaporated, are presently embodied in two principal forms, namely; either with vanes which are rigidly secured to the rotor or with stirring paddles or wiper blades which are movably secured thereto.

Evaporators constructed with rigid rotor blades deposit a fluid film on the heated wall of the housing at a thickness corresponding approximately to the play or spacing between the outer edge of the rotor blades and the inner wall of the housing. Since the quantity of fluid material which flows per second in a longitudinal direction and vertically through a transverse cross-sectional area of the housing must be greater than the nominal flow rate or .volume per unit time at this-cross-sectional area (i.e., the flow rate determined by the film thickness, the circumference of the film and the average fluid layer velocity in the axial direction) in order to achieve a direct influence on the fluid film by the rigid rotor vanes, evaporators of such type are relatively limited in the quantity or throughput of fluid material which they can adequately handle. That is, in order to receive direct processing influence from the action of rigid rotor vanes, the throughput of material being processed must be great enough to exceed somewhat the theoretical throughput that would be just suflicient to fill the annular clearance space described between the rotor vanes when rotatthe inner surface of the processing chamber, for unless the throughput is great enough to provide such excess the fluid film is not maintained sufllciently thick for active contact by the outer edges of the rotor vanes. However, as long as the rigid rotor blades are able to remain in contact with the fluid film, they can influence an intensive turbulence by virtue of theformed wavelike fluid crests and the rotation of the edge of the rotor blading, which considerably increases the rate of heat exchange of the heated housing wall in comparison with an essentially free-falling film. The increased turbulence permits a considerably greater heat transfer per unit surface even with heat sensitive products, without resulting in damage to such products by virtue of the increased temperature of the heated wall.

ln'determining the minimum spacing between the edges of the rigid rotor blading and the wall of the housing, it is not only necessary to take into consideration the assembly tolerances obtainable in actual practice, but it is also necessary to consider the different heat'expansion characteristics or" the rotor and the housing, such is especiall'ytrue since in actual practice when the installation is started and stopped, the aforedescribed thermal expansion can easily occur. As soon as, however, the thickness of the fluid film is reduced and falls below a given amount, as would occur when an evaporation process or other specific reaction takes place, then the rigid rotor blades will no longer contact with their edges the fluid film. Consequently, there exists the danger that there will result at least a partial demoistening or dry zone of the heated surface, especially in the lower region of the apparatus. The thus produced intensive evaporation process resulting from the high thermal stress results, on the other hand, that spatters are dislodged by the vapors from the outer surface of the fluid medium. If the rotor element is now so constructed that the blades extend from the shaft of the rotor to the layer of fluid film and such blades are formed without any larger recesses or the like, then the thus constructed rotor blading will work along the length of the evaporator in the manner of a separator, and in such a manner that the dislodged droplets or fluid particles will again be thrown or directed back into the fluid film by the centrifugal forces.

In the construction employing relative movable wiper blades, these blades are normally so constructed that their center of gravity is displacedrelative to the pivot axis, such that said wiper blades are pressed against the surface of the housing under the influence of the centrifugal forces. The fluid fllm resulting therefrom is a function of the quantity of fluid medium appearing at such location, its viscosity and the centrifugal forces applied to the film layer through the intermediary of the wiper blades. However, in such type of wiper blade construction, the maximum quantity of fluid medium which can be handled is considerably limited in that the largest pos sible thickness of the film layer is limited by the radial expansion of the wiper blades. Larger quantities of fluid material will merely fall untreated through the evaporator. Additionally, the relatively movable wiper blades, which for the most part merely glide over the surface of the fluid film, are not able to achieve as intensive a fluid turbulence as the rigid rotor blades. Consequently, the layer of fluid medium isnot replenished or renewed on the wall surface of the housing to the same degree as when employing rigid rotor blading, whereby also the heat exchange capacity changes.

areas?- It has alread been ro osed with eva orators em- Y P is and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the achieve a reduction of the thickness of the fluid layer in the axial flow direction of the apparatus. Also here there results the disadvantages which accompany all such evaporators provided with movable Wiper blades that, on the one hand, a relatively small turbulence is produced, while on the other hand, in view of the limited radial expansion or extension of the wiper blades, which are normally mounted in a frame structure, the above-mentioned separation effect is very limited.

Accordingly, it is an important object of the present invention to provide a processing apparatus, such as an evaporator of the type as heretofore described, which embodies the advantageous characteristics of the known evaporators while simultaneously obviating the disadvantageous thereof.

Another important object of the present invention'is to provide an apparatus for the processing of fluid materials in an efficient and reliable manner and which permits for an effective heat exchange between the wall of the housing and the material distributed thereon in the form of a fluid film.

Still another important object of the present invention is to provide a processin apparatus which is economical to manufacture, easy to assemble and disassemble, as well as being easy to clean and service.

Yet another important object of t.e present invention is to provide a novel rotor structure for a material processing apparatus comprising both relatively fixed and relatively movable rotor vanes.

A further important object of the present invention is to provide a novel rotor construction which effectively causes distribution of the material to be handled in a film-like manner on the wall of the housing of the processing apparatus, redistributes dislodge-d fiuid particles back onto said housing wall, effectively works throughout the entire heat transfer zone of the housing, and can be assembled and disassembled in a relatively simplified manner.

The evaporator designed according to the teachings of the present invention is provided with the feature that in the region of the wall of the housing where the larger thickness of the layer of the material to be processed appears, the rotor blades are rigidly constructed and spaced from the wall of the housing, whereas the vanes located in the region of the housing where there appears a smaller thickness of the fluid layers are constructed so as to give and be relatively movable and are adapted to be urged or driven toward the wall of the housing.

In one preferred constructional form of rotor, the wiper blades in fully extended radial position possess a radial dimension measured from the rotor axis which is greater than the radial distance to the inner housing wall. As a result. when the rotor is assembled in the housing and the device is in operation, the wiper blades will trail the fixed rotor blades and will be continuously urged into surface contact with the fluid layer irrespective of its thickness. In another form of rotor construction, the movable wiper blades, even in their most radial extended position still provide a relatively small clearance at their tip end from the inner wall of the housing of the apparatus.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

In the drawing:

FIG. 1 schematically illustrates a longitudinal, elevational view of an evaporator designed according to the teachings of the present invention, with a portion of the Wall thereof removed to reveal the interior rotor thereof it appears at rest;

P16. 2 is an enlarged, cross-sectional view of the evaporator shown in FIG. 1 and taken along lines lI-II thereof, but showing the rotor as it appears when rotating as indicated by the FIG. 2 directional arrow;

FIG. 3 is an enlarged, fragmentary view of a portion of the rotor blading employed in the evaporator of FIG. 1 substantially as seen from the section line IIIIII in FIG. 2; and

FIG. 4 is a fragmentary sectional view of a variant construction of the rotor blading employed in the embodiment of the processing apparatus illustrated in FIGS. 1-3, substantially as would be seen at the section line lV-IV in FIG. 1 when the rotor is rotating as indicated by the FIG. 4 directional arrow.

Referring now to the drawing and, more particularly, to FIGS. 1-3 thereof, there is illustrated an apparatus for processing different kinds of fluid materials or the like, such as an evaporator, generally designated by the refer ence numeral 1. The evaporator 1 is provided with a suitable longitudinally extending evaporator housing or tubular casing 5, at the upper end of which there is mounted a separator unit 2. A rotatable rotor member 3 is mounted internally of the evaporator housing 5 and is rotatably supported at its lower end in a bearing 4 located at the lower end In of the evaporator 1. It will thus be appreciated that the rotor member 3 is enclosed by the evaporator housing 5 and is driven by a suitable drive motor 3a via pulley means 312. At the lower end 1:; of the evaporator housing 5 there is arranged an outlet member 6 for the non-vaporized residue or material. Adjacent the upper end lb of the evaporator 1 there is provided a supply conduit 7 for supplying the fluid medium or the like which is to be evaporated. The evaporafor housing 5 is encompassed by a suitable temperature exchange arrangement, such as a heating jacket formed of the double-section members 8 and 9 which are arranged endwise to one another in the axial direction of the evaporator housing 5. Each of the heating section members 8 and 9 are provided with a delivery flange 11 and a discharge flange 12 for the supply and return of a suitable heat exchange medium to the heating jacket members 8 and 5. Naturally, depending upon the desired use of the apparatus, the temperature exchange means 8, 9 may be designed to cool the material deposited upon the housing wall 5a.

As can be clearly seen from FIG. 1 and the crosssectional view of FIG. 2, the rotor member 3 is formed as a star-shaped member possessing three equidistantly spaced elongated blades or fins 13 including an upper vane portion 13b which extends almost to the inner wall 5a of the evaporator housing 5 in the upper region of said housing surrounded by the heating jacket portion 8. The blades and in particular the upper vane portion 131) are spaced from the inner wall 5a of the evaporator housing 5 a predetermined amount to provide a suitable clearance or space tolerance therebetween, the magnitude of which is selected to take into account the fitting toleranccs during assembly of the device, as Well as the dif ferent thermal expansion of the rotor 3 and the housing 5 of the evaporator 1. Naturally, the teachings of the present invention are not limited to a rotor construction possessing three blades, as other blade numbers are obviously contemplated.

In the lower region of the evaporator housing 5 surrounded by the heating jacket portion 9, the blade members 13 are each provided with a necked or recessed portion 14 to define the lower vane portion 13:: which is of smaller Width than the respectiveupper vane portion 13b of the blades 13. Attached to the inwardly necked and smaller width, vane portions 13a are the axially and radially movable wiper blades 16. As can more clearly be seen in FIGS. 3 and 4 the wiper blades 16 and recessed blade portions 13a are provided with suitably formed slots or cutouts 2i) and 21, respectively, adapted to detachably receive the respective ring-shaped articulating or connecting members 15, which piercingly extend through the wiper blades 16.

It will thus be appreciated that the rotatable rotor member 3 is constructed to possess a hub portion 3a and the rigid'blades 13 which carry at their lower vane portions 13a, the relatively movable wiper blades 16. Thus, each blade 13 of the rotor is constituted by an elongated body member having an upper vane portion 13b and a lower vane portion 13a, said vane portion 13a being of smaller radial extent than the upper vane portion 13b and integral therewith. At the lower vane portion 13a there are suitably connected the relatively movable wiper blades 16 which can move in both the radial and axial directions, as will be more fully described hereinafter.

As previously mentioned, the wiper blades 16 are provided with the slots 20 and the lower vane portions 13a with the slots 21 for suitably receiving the connecting members in such a manner as to afford these connecting members a certain degree of play. In order to prevent a dislodging or separation of the connecting means 15 from their associated slots 20, 21 there is provided, by way of example, suitable retaining or holding plates 22 and 23 (FIGS. 3 and 4). As can be seen from the drawing, the retaining plates 22, 23 are respectively fastened to the movable wiper blades 16 (or 16'), and to the lower rotor vane portion 13a, at a certain required distance from the connecting member 15 so as not to interfere with the desired degree of play or movement thereof.

By virtue of the afore-described arrangement of the connecting means 15 between the wiper blades 16 and the lower reduced vane portions 13a there is achieved, in addition to the swivable or pivotable movement of said wiper blades 16, an axial movement thereof. Thus, in the rest position of the rotor 3 the wiper blades 16 can move downwardly, as clearly shown in phantom in FIG. 3, and are suspended by the connecting members 15 in such a manner that a relatively larger space is formed between the outer edge 16a of the wiper blades 16 and the opposed inner wall 5a of the evaporator housing 5. Due to the formation of the reduced vane portions 13b by necking of each blade member 13 at the recessed portion 14, the rotor 3 can be assembled and disassembled from the evaporator housing 5, as for example during cleaning thereof, in a relatively simple manner, whereby the danger that the wiper blades 16 will become damaged as by twisting or otherwise is effectively minimized or prevented.

In the embodiment shown in FIGS. 1-3, the width of the wiper blades 16 is so chosen that when the wiper blades 16 are brought into their complete extended position in the radial direction of the lower blade portions 13a, that is to say, prior to assembly within the housing 5, the distance between the outer edge 16a of the wiper blades 16 and the axis of rotation of the rotor 3 is greater than the radial distance from said axis of rotation to the inner wall 5a of the evaporator housing 5. Thus, the rotor member 3 when assembled in the evaporator housing 5 will exhibit rearwardly directed wiper blades 15, when viewed with respect to the direction of rotation of the rotor 3 as denoted by the arrow A of FIG. 2, so that the wiper blades 16 trail the rigid vane portions 13a and 13]; during the operation of the apparatus.

During the operation of the evaporator 1 the fluid in'a dium received from the. supply conduit 7 isfuniformly distributed on the inner wall. 5a of the evaporator housing 5 by means of the rotor blades 13. By suitably measuring or controlling the incoming quantity of fluid medium, it, is :possible to ensure that the thickness of the fluid layer or film in' the region of the inlet to the evaporator housing 5, and which is distributedonto the inner wall 5a thereof, approximates or is slightly larger than the spacing between the free end 13c of the vane portion 13b and the inner wall 511 of the evaporator housing 5. On the other hand, the thickness of the fluid filmor'layer continuously decreases as such'fil mmoves downwardly away from the supply conduit 7, and at the lower end of the rotor 3 forms a fluid layer mass which is smaller than the afore-described spacing between the blade edge 13c and inner housing Wall 5a.

In reach ofthe fluid layer of reduced thickness "are the superimposed wiper; blades 16, arranged for example in two juxtapositioned rows, which during the rotational movement of the rotor 3 are driven under the influence of the applied centrifugalforces against the inner wall 54: of the evaporator housing 5 and into surface contact with the reduced thickness film layer. As a result, the fluid film is acted upon throughout the "entire lengthlof the evaporator 1 by the rigid vane'members 13b and the relatively movable axially oriented wiper blades 16, the latter of which may difler in length from one another. Since the rotor member 3 is formedthroughout its entire length by continuous blade portions 13a, 1%,, there results during the rotation thereof, an effective separation of the'fluid droplets or particles which are carried upwardly by the rising vapor mass. Consequently, rotor member 3 exhibits the workings of a second separrator which is serially connected to the actual separator unit 2. V

Due to the strong turbulence of the layer of fluid medium produced by the rigid vanes 13b, an intensive heat exchange effect is produced. For this reason it is also possible to maintain the thermal energy of .the heating jacket 8 in the region of the rigid vanes 13b greater than that of the heating jacket 9 in whose region the movable wiper blades 16 are arranged.

In the variant constructional form illustrated in FIG. 4, there is depicted a rotor construction 3 in which the relatively movable wiper blades 16' are constructed to possess such a width that the outermost edge 18 can extend very close to the inner Wall 5a of the evaporator housing 5 without, however, scraping there against. Such constructed Wiper blades 16' may be formed of a relatively thick sheet or plate, which during the operation of the'apparatus and by virtue of its large mass is urged with a large force into a radial extended position, with- ;out however contacting the housing wall 5a. The use and arrangement of blades having this variant constructional form are described at furtherlength and claimed in copending application Serial No. 234,505, filed'October 31, 1962.

Naturally, it is equally possible to connect the wiper blades '16 to the vane portions 13a, byway of example, with oval-shaped connecting means, hinges or the like, instead of with the ring-shaped connecting members previously described. It is only necessary, of course, that the wiper blades 16 be articulated at the extended, reduced width, lower vane portion 13a of the blades 13, and in such a manner as to be relativelymovable with respect to the rigid vane portions 13a and 13b of the rotor blading 13.

In the disclosed embodiments of the present invention there is achieved that the rotor member throughout its entire length is effective as a separator element. Such is true, even if the rotor vanes are provided with perforations or cutouts. It is further not absolutely necessary that the heating or cooling jacket portions extend over the entire length of the housing of the apparatuspThus,

it is possible that only a portion of the housing 5 is heated or cooled. It is equally possible to have the arrangement of the apparatus such that a portion of the housing is heated, while another portion thereof is cooled.

The described suspension or mounting of the relatively movable wiper blades in the elongated necked portion of the rotor blades has, in all instances, theadvantage of making it unnecessary to provide lateral mountings or support frames which would obstruct and interrupt the vacant or free cross-sectional area in the housing chamber. Consequently, there results, in contradistinction to the known wiper blade constructions, no danger that there will be a depositing or sedimentation of material on the mounting members for the wiper blades, which would either prevent, or make extremely difficult, a continuous operation of the apparatus as well as contaminating the product.

It is to be appreciated that the apparatus described herein need not be restricted solely to a vertically arranged housing and thus, the terms upper and lower as employed herein are to be understood in their broader sense to indicate in a general way the direction of flow of the fluent material through the processing apparatus. While in a preferred embodiment of the invention the fiow direction is essentially influenced by gravity, it is possible to arrange the structure described horizontally with its longitudinal axis lying in a substantially horizontal direction. In such a case, the term upper or upper portion as employed herein indicates the region of entry of the material and lower or lower portion denotes the region of efflux of the material. In such an arrangement,

the moving film can be influenced by forces other than gravity, as for instance centrifugal forces. Further, it is to be appreciated that the term contact as used herein is not restricted only to an actual physical contact of the blading means with the fluent material, and is also employed in the sense of indirect contact or influencing the fluid film through air or otherwise which may be disposed between the edge of the blading and said film.

It will thus be apparent that the material processing apparatus of the present invention is readily suitable for continuously processing fluids in a variety of ways. Thus, the apparatus may be employed, by way or" example, as an evaporating and concentrating apparatus, orfor distillation of liquids or in any other manner which will readily suggest itself to those skilled in the art. It will further be evident that the invention is readily adapted for carrying out exothermic and endothermic reactions.

Having thus described the nature of the present invention what is desired to be secured by United States letters Patent is:

1. In apparatus for processing fluent material in thin layer form; a housing having inner wall portions defining a fluent material processing zone extending from an inlet region to an outlet region, means for providing heat transfer through the inner housing wall portions at said processing zone, means for directing the delivery of fluent material to said processing zone at said inlet region, rotor means disposed within said housing at said processing zone, drive means for rotating said rotor means to cause layer forming action thereby within said processing zone, said rotor means including elongated upstream and downstream vane portions that are rigidly supported and extend integrally through said processing zone, the upstream vane portion presenting a relatively fixed outer edge portion thereof for layer forming action in spaced relation to said inner housing wall portions adjacent the inlet region of said processing zone, the downstream vane portion being of lesser radial extent so as to present a relatively fixed outer edge portion thereof in substantially greater spaced relation to said inner housing wall portions than said upstream vane portion, and said downstream vane portion carrying at least one wiper blade element for layerforming action at said inner housing wall portions under the influence of centrifugal force adjacent the outlet region of said processing zone.

2. In apparatus for processing fluent material in thin layer form; the structure defined in claim It and further characterized in that said wiper blade element is carried at said downstream vane portion by connecting means respectively engaging said vane portion and wiper blade element so that the latter is swiveled axially as well as being radially movable with respect to the former, and in that the radial extent of said wiper blade element is such as to dispose the outer edge thereof for a dragging layer forming action at said inner housing wall portions under said centrifugal force influence.

3. In a rotor structure for layer forming action within apparatus for processing fluent material in thin layer form; a rotor hub, a plurality of elongated blade members supported rigidly by said rotor hub, and each of said blade members having a first lengthwise vane portion presenting a relatively fixed outer edge and a second continuing lengthwise vane portion having a lesser radial extent and carrying a relatively movable wiper blade element, the fully extended radial extent of said wiper blade element and said second vane portion exceeding the radial extent of said first vane portion.

4. A layer forming blade structure for use in apparatus arranged to process fluent material in thin layer form; said blade structure comprising a first lengthwise vane portion presenting a relatively fixed layer forming edge, and a second continuing lengthwise vane portion having a lesser radial extent and carrying a relatively movable wiper blade element for succeeding differential layer forming action in relation to the fixed edge of said first vane portion.

5. In apparatus for processing fluent material in thin layer form; a housing having wall portions defining a fluent material processing zone, means for providing heat transfer through the housing Wall at said processing zone, rotor means mounted for layer forming rotation within said housing, drive means for rotating said rotor means, said rotor means including an elongated rigidly supported blade structure extending through said processing zone with a first lengthwise vane portion thereof presenting a relatively fixed layer forming edge at the housing wall, and with a second continuing lengthwise vane portion thereof carrying at least one relatively movable wiper blade element for layer forming action at said housing wall, said wiper blade element being carried at said second vane portion by annular members received and retained freely within respective apertures provided in said second vane portion and said wiper blade element so that the latter is rendered both axially and radially movable with respect to the former.

References (Iitcd by the Examiner UNITED STATES PATENTS 1,576,338 3/26 Mellott 159--6 2,175,406 10/39 Osborn 15104.l4 2,542,269 2/51 Zahm 159-6 2,542,270 2/51 Zahm 195-6 2,546,381 3/51 Zahm l596 2,974,725 3/61 Samesreuther et al. 159-6 FOREEGN P TENTS 1,061,293 7/59 Germany.

NORMAN YUDKOFF, Primary Examiner.

CHARLES OCONNELL, Examiner. 

1. IN APPARATUS FOR PROCESSING FLUENT MATERIAL IN THIN LAYER FORM; A HOUSING HAVING INNER WALL PROTIONS DEFINING A FLUENT MATERIAL PROCESSING ZONE EXTENDING FROM AN INLET REGION TO AN OUTLET REGION, MEANS FOR PROVIDING HEAT TRANSFER THROUGH THE INNER HOUSING WALL PORTIONS AT SAID PROCESSING ZONE, MEANS FOR DIRECTING THE DELIVERY OF FLUENT MATERIAL TO SAID PROCESSING ZONE AT SAID INLET REGION, ROTOR MEANS DISPOSED WITHIN SAID HOUSING AT SAID PROCESSING ZONE, DRIVE MEANS FOR ROTATING SAID ROTOR MEANS TO CAUSE LAYER FORMING ACTION THEREBY WITHIN SAID PROCESSING ZONE, SAID ROTOR MEANS INCLUDING ELONGATED UPSTREAM AND DOWNSTREAM VANE PORTIONS THAT ARE RIGIDLY SUPPORTED AND EXTEND INTEGRALLY THROUGH SAID PROCESSING ZONE, THE UPSTREAM VANE PORTION PRESENTING A RELATIVELY FIXED OUTER EDGE PORTION THEREOF FOR LAYER FORMING ACTION IN SPACED RELATION TO SAID INNER HOUSING WALL PORTIONS ADJACENT THE INLET REGION OF SAID PROCESSING ZONE, THE DOWNSTREAM VANE PORTION BEING OF LESSER RADIAL EXTENT SO AS TO PRESENT A RELATIVELY FIXED OUTER EDGE PORTION THEREOF IN SUBSTANTIALLY GREATER SPACED RELATION TO SAID INNER HOUSING WALL PORTIONS THAN SAID UPSTREAM VANE PORTION, AND SAID DOWNSTREAM VANE PORTION CARRYING AT LEAST ONE WIPER BLADE ELEMENT FOR LAYER FORMING ACTION AT SAID INNER HOUSING WALL PORTIONS UNDER THE INFLUENCE OF CENTRIFUGAL FORCE ADJACENT THE OUTLET REGION OF SAID PROCESSING ZONE. 